Git init
git init is used to initialize a new git repository from current working directory.
This command creates a new hidden subdirectory named .git
If you want to stop git, just remove this folder.
Git status
git status shows the status of changes as untracked, modified, or staged.
Understanding Git Status
git status provides information about the state of your working directory and staging area. Here are the key terms:
Git log
git log shows the history of commits and its corresponding hashes.
git loggit log --oneline # brief view
Stage files
git add stages files for commit.
git add < filename> # stage specific files git add . # stage all files (tracked / untracked) git add -A # stage all (including parent and subfolders) git add -u # stage only tracked files (modified, deleted)
Git reset (Unstaging)
git reset unstages all files and folders you added.
Make commit
git commit creates your project’s version , or a hash block .
You should provide message folling -m, that describes the version.
Consider committing a serious process of your job, like signing a doc.
git commit -m "Commit message, describes the work / version"
Git reset 2
git reset also can reset your previous commit.
You should mention the hash (id) of commit.
HEAD is a pointer where you are currently at.HEAD~1 means 1 commit before current hash (version).
Set Remote repository
The process so far is only for your local version management, which is also completely fine for local work.
However, you can also make your repository “Synchronized” to a cloud server: Github.
git remote add adds remote repository.
origin is naming convention for Github remote repo.main is your local branch name.
Let’s check the branch names first.
Exercise: Check branch
Let’s check the current local branch name. We use main branch named as “main”.
If your local branch name is not main (i.e. master or etc), change it to main with below command.
git branch -M main # Force move branch named as main
Add remote repository
Now we can add remote repository with following command.
git remote add < remote_name> < remote_url> # example: Remote Repo named as origin git remote add origin https://github.com/username/repositoryname
Push to repository
git push sends your commit to the remote repository.
# When pushing for the first time git push -u origin main # From then git push
Exercise
Let’s push your local classrom git to the github.
Check first: 1) Your local status is clean (check with git status) 2) If not clean (You made edit after the initial version) stage changes and commit.
Then type below to push:
Homework
Browse your github site, and see files are uploaded.
https://github.com/yourGithubId/Reponame.git
By default, git will only track files, not empty folders. Folders are tracked when files are in it.
Git clone
What if you wanted to download someone else’s remote repository to your local machine? Git clone is for the first time downloading from the remote repository.
git clone < repo_url> # example git clone https://github.com/example-user/example-repo.git
Exercise
Now let’s clone OUR CLASS repository (that I upload all class materials).
git clone action will create a folder and download everything from the upstream.
You should make a separate folder apart from your own class folder
Move one folder up from your class folder when you clone it.
Example: if your class folder address is ~/my_fin4770 then you should clone it from ~.
# Copy our class repository address below. git clone https://github.com/INSTITUTION/CLASS-REPO.Git
Pull from repository
git pull downloads and apply changes from the repote repository.
Actually, git pull does two things altogether:
fetch: download changes, but not apply the changes to local
If you want to see the differences between the two.
merge: apply changes to your local file
In-class Exercise
Now, I will make modify and update the class repositroy.
After the update, use git pull from the local class repo to apply the update.
Github and IDE
When using github from other apps (e.g. Positron , VScode , etc), you’ll use PAT (personal access token) instead of password.
Generate token from the github page, possibly with no expiration (or long enough)
Copy the token to clipboard (you won’t see the token again)
Store it somewhere temporarily
Three pull method
By default, git pull is
git fetch # download update but do not apply changes to local git merge # merge changes git pull has three methods:
git mergeCombines changes into a new merge commit. You will need to combine and resolve conflicts.
B, C are your local change
Example: Git merge scenario
Content of file.txt
Alice edits the second line and commits and push to main first:
Bob also edits the same line, but did not pull Alice’s changes. He edits and commits locally:
When Bob tries to push changes with git push, Git will reject because his local branch is behind the remote.
Bob runs git pull which is git fetch and git merge: git shows the conflicts
The file.txt now contains conflict markers
To resolve conflict, Bob should modify the file manually.
Bob stages this file and commits the resolution:
After resolving, Bob pushes with git push.
git rebaseGit replays your local branch on top of the remote branch, creating a linear history:
Example: Git rebase scenario
Content of file.txt
Alice edits the second line and commits and push to main first:
Bob also edits the same line, but did not pull Alice’s changes. He edits and commits locally:
When Bob tries to push changes with git push, Git will reject because his local branch is behind the remote.
Bob runs git pull --rebase which is git fetch and git rebase:
Instead of creating a merge commit,
When there’s no conflict, (i.e., they did not change the same line of code) git pull –-rebase won’t raise any conflict message.
However, in our scenario, there’s conflict since both modified the same line, so:
Similar to merge, conflict should be resolved manually.
The file.txt now contains conflict markers
To resolve conflict, Bob should modify the file manually.
Bob stages this file and continues the rebase (no commit)
git add file.txtgit rebase --continue
After that Bob pushes with git push. The history is linear.
git merge --ff-onlyUsed when you expect no conflicts.
When you want linear history and want to move your local branch pointer forward without modifying.
Git rejects if there is any conflict
.gitignore
Git keep tracks all changes within the project directory
If there are files/folder you don’t want to track , specify them in .gitignore file.
git clean
If you want to remove untracked (not unstaged!) files:
git clean -nd # dry run (show what will be removed) git clean -df # remove untracked files
